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Pope Sylvester II tried to introduce Arabic numbers into Europe between the years 999 and 1003, but their use did not catch on for a few more centuries, and Roman numerals continued to be the primary number system.

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Long-term mental and physical effects from substance abuse include: paranoia, psychosis, immune deficiencies, and organ damage.

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Cyanide works by making the human body unable to use oxygen.

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Autoimmune diseases occur when the immune system destroys its own healthy tissues. When this occurs, white blood cells cannot distinguish between pathogens and normal cells.

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Human stomach acid is strong enough to dissolve small pieces of metal such as razor blades or staples.

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